Does a diverse whole-food plant-based dietary intervention improve gut microbiome composition, gut symptoms, energy and hunger in healthy adults? A randomised controlled trial.

Diets low in diverse fibre-rich plant foods contribute to the rise of chronic disease. The BIOME study (NCT06231706; 6-week parallel randomised controlled trial) in 399 adults (35-65 years; BMI 18·5-40 kg/m2; fibre intake < 20 g/d) investigated a whole-food plant blend containing > 30 ingredients, rich in (poly)phenols, fibre and micronutrients. Participants were randomised (1:1:1) to the blend (30 g/d), an isoenergetic control (bread croutons, 28 g/d) or probiotic (Lactobacillus rhamnosus, 15bn CFU/d). Analysts were blinded to allocation. The primary outcome was change in 'favourable' and 'unfavourable' gut microbiome species (ZOE Microbiome Health Ranking 2025); secondary outcomes included blood metabolites, symptoms, stool output, anthropometry, hunger, sleep, energy and mood. A crossover sub-study explored postprandial glucose, hunger and mood. Of 349 participants analysed (fifty excluded), self-reported adherence was > 98 %. The 30+ plant blend resulted in more species changing relative abundance at 6 weeks v. control (57 v. 14 species-level genome bins (SGB), P < 0·001) and probiotic (57 v. 4 SGB, P < 0·001). There were no significant between-group differences in microbiome health ranks of significantly changing species (increasing or decreasing). Blend participants self-reported reduced indigestion, constipation, heartburn and flatulence and increased energy v. control (all P < 0·05). Six related but no serious adverse events occurred. In the sub-study, adding the blend to a high-carbohydrate meal (v. meal alone) reduced hunger, increased fullness and energy (3-h incremental AUC, all P < 0·05), with no effect on postprandial glucose. This 30+ plant blend represents a simple strategy to modify gut microbiome composition and benefit gastrointestinal symptoms in healthy adults.